A PDC or a GSM (registered trademark), both of which are related-art public wireless communication networks, uses low frequency bands, and hence text-based communications such as emails or small-size web pages, have been mainstream of communications of mobile terminals. The 3G standard, the HSPA (High Speed Packet Access) standard, the LTE (Long Term Evolution) standard, the WiMAX standard, or the like, has recently been put into practice, and the band of the public wireless communication network has become wider accordingly. For these reasons, in addition to being able to browse a web page, the volume of which is equivalent to a web page which is browsed by use of a personal computer connected to the Internet by means of a cable, the mobile terminal can carry out communication of a large volume of data such as images and sounds. In particular, in relation to an HSUPA (High Speed Uplink Packet Access), the LTE, or the WiMAX standard, a so-called uplink communication frequency band from a mobile terminal toward a base station is also broadened. Therefore, data such as images and sounds can be uploaded by means of real-time streaming in addition to downloading by means of real-time streaming. Consequently, application of the wireless communication to a TV phone or a TV conference using mobile terminals, a live broadcast from the spot by way of a public wireless communication network, and the like, has been conceived.
In the meantime, although the maximum uplink frequency band of the public wireless communication network can be set to 1 Mbps to about 37 Mbps that are equal to the maximum frequency bands of a wired communication network, the wireless communication, contrary to the wired communication network, is susceptible to variations in radio environment according to various conditions. For this reason, a communication is not always practicable at the maximum frequency band in the public wireless communication network all the time. In short, the communication standards, except the 3G standard, adopt a so-called best effort communication that distributes a fixed frequency band to users around a base station. For this reason, the larger the number of users located around a base station, the smaller the frequency band allocated to each user. In addition, communication quality such as a frequency band, a packet loss rate and a delay, varies under various conditions, such as influence of handover stemming from traveling of the user and influence of fading caused by surrounding buildings.
Consequently, if the frequency band drops to 1 Mbps for reasons of fluctuations in radio environment, or the like, when the mobile terminal is in the course of transmitting image data in real time at; for instance, 5.7 Mbps that is the maximum frequency band of the HSUPA, images will be interrupted on a receiver side. The mobile terminal must take measures, such as transmitting the image data at a higher compression rate; for instance, 1 Mbps, and the like. In addition, when communication quality is poor, a user of the mobile terminal must attempt to improve the radio environment by changing his/her location, in addition to the data compression rate being changed by the mobile terminal.
In order to take measures conforming to the radio environment, such as those mentioned above, it is necessary for the mobile terminal on the transmission side to grasp communication quality of the public communication network. Therefore, when the mobile terminal transmits data, such as images and sounds, by means of real-time streaming, it is very critical for the communication terminal to acquire communication quality reflecting the radio environment.
Patent Literature 1 describes a technique for presenting a receiving state of a communication party on the other end to the user of the communication terminal. FIG. 17 is a diagram showing an example internal configuration of a network terminal described in Patent Literature 1. In a terminal 103, data encoded by an encoder 201 are transmitted to a terminal 105 by way of a transmission buffer 203, and simultaneously accumulated in a local buffer 205. Subsequently, a reproduction image quality determination section 221 in the terminal 105 determines quality of a reproduced image during reproduction of received data. On occasion of determination of quality of a reproduced image, the image quality of a reproduced image may differ from image quality achieved at transmission, under influence of a packet loss during transmission/reception of data. Reproduction image quality information including the influence is fed back from the terminal 105 to the terminal 103. The terminal 103 decodes and reproduces the data accumulated in the local buffer 205 in accordance with the reproduction image quality information. The image can thereby be reproduced on the terminal 103 at the same quality as that of an image actually reproduced by the terminal 105. The user of the terminal 103 can attempt to optimize image quality by changing control of parameters and a location of the terminal 103 (i.e., the location of the terminal 103) in accordance with the image quality.